
/* @(#)w_jn.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/*
 * wrapper jn(int n, double x), yn(int n, double x)
 * floating point Bessel's function of the 1st and 2nd kind
 * of order n
 *
 * Special cases:
 *  y0(0)=y1(0)=yn(n,0) = -inf with division by zero signal;
 *  y0(-ve)=y1(-ve)=yn(n,-ve) are NaN with invalid signal.
 * Note 2. About jn(n,x), yn(n,x)
 *  For n=0, j0(x) is called,
 *  for n=1, j1(x) is called,
 *  for n<x, forward recursion us used starting
 *  from values of j0(x) and j1(x).
 *  for n>x, a continued fraction approximation to
 *  j(n,x)/j(n-1,x) is evaluated and then backward
 *  recursion is used starting from a supposed value
 *  for j(n,x). The resulting value of j(0,x) is
 *  compared with the actual value to correct the
 *  supposed value of j(n,x).
 *
 *  yn(n,x) is similar in all respects, except
 *  that forward recursion is used for all
 *  values of n>1.
 *
 */

#include "fdlibm.h"
#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
    double jn(int n, double x)  /* wrapper jn */
#else
    double jn(n,x)          /* wrapper jn */
    double x; int n;
#endif
{
#ifdef _IEEE_LIBM
    return __ieee754_jn(n,x);
#else
    double z;
    struct exception exc;
    z = __ieee754_jn(n,x);
    if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
    if(fabs(x)>X_TLOSS) {
        /* jn(|x|>X_TLOSS) */
            exc.type = TLOSS;
            exc.name = "jn";
        exc.err = 0;
        exc.arg1 = n;
        exc.arg2 = x;
            exc.retval = 0.0;
            if (_LIB_VERSION == _POSIX_)
                Djy_SaveLastError(ERANGE);
            else if (!matherr(&exc)) {
               Djy_SaveLastError(ERANGE);
            }
        if (exc.err != 0)
           Djy_SaveLastError(exc.err);
            return exc.retval;
    } else
        return z;
#endif
}

#ifdef __STDC__
    double yn(int n, double x)  /* wrapper yn */
#else
    double yn(n,x)          /* wrapper yn */
    double x; int n;
#endif
{
#ifdef _IEEE_LIBM
    return __ieee754_yn(n,x);
#else
    double z;
    struct exception exc;
    z = __ieee754_yn(n,x);
    if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
        if(x <= 0.0){
        /* yn(n,0) = -inf or yn(x<0) = NaN */
#ifndef HUGE_VAL
#define HUGE_VAL inf
        double inf = 0.0;

        SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */
#endif
        exc.type = DOMAIN;  /* should be SING for IEEE */
        exc.name = "yn";
        exc.err = 0;
        exc.arg1 = n;
        exc.arg2 = x;
        if (_LIB_VERSION == _SVID_)
            exc.retval = -HUGE;
        else
            exc.retval = -HUGE_VAL;
        if (_LIB_VERSION == _POSIX_)
            Djy_SaveLastError(EDOM);
        else if (!matherr(&exc)) {
            Djy_SaveLastError(EDOM);
        }
        if (exc.err != 0)
           Djy_SaveLastError(exc.err);
            return exc.retval;
        }
    if(x>X_TLOSS) {
        /* yn(x>X_TLOSS) */
            exc.type = TLOSS;
            exc.name = "yn";
        exc.err = 0;
        exc.arg1 = n;
        exc.arg2 = x;
            exc.retval = 0.0;
            if (_LIB_VERSION == _POSIX_)
                Djy_SaveLastError(ERANGE);
            else if (!matherr(&exc)) {
                Djy_SaveLastError(ERANGE);
            }
        if (exc.err != 0)
           Djy_SaveLastError(exc.err);
            return exc.retval;
    } else
        return z;
#endif
}

#endif /* defined(_DOUBLE_IS_32BITS) */
